Method for manufacturing display device and substrate for manufacturing display device

ABSTRACT

Discussed is an assembly substrate used for a display device manufacturing method of mounting semiconductor light-emitting diodes on the assembly substrate at preset positions using electric field and magnetic field. The assembly substrate includes a base portion, a plurality of assembly electrodes on the base portion, a dielectric layer on the base portion to cover the assembly electrodes, a barrier wall on the base portion, and a metal shielding layer on the base portion, wherein the metal shielding layer overlaps the barrier wall.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is a Continuation of U.S. patent application Ser. No.16/834,315, filed on Mar. 30, 2020 (now U.S. Pat. No. 11,211,366, issuedon Dec. 28, 2021), which claims the benefit of an earlier filing date ofand the right of priority under 35 U.S.C. § 119(a) to Korean ApplicationNo. 10-2019-0068834, filed on Jun. 11, 2019, the entire contents ofthese applications are hereby expressly incorporated by reference hereinin its entirety into the present application.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

The present disclosure relates to a method for manufacturing a displaydevice, and more particularly, to a method for manufacturing a displaydevice using semiconductor light-emitting diodes of several micrometers(μm) to several tens of micrometers, and an assembly substrate used formanufacturing a display device.

2. Background of the Related Art

In recent years, in the field of display technology, liquid-crystaldisplays (LCD), organic light-emitting diode (OLED) displays, microLEDdisplays, etc. have been competing to realize large-area displays.

Meanwhile, semiconductor microLEDs (μLED) with a diameter orcross-sectional area less than 100 microns, when used in displays, mayoffer very high efficiency because the displays do not need a polarizerto absorb light. However, large-scale displays require several millionsof semiconductor light-emitting diodes, which makes it difficult totransfer the devices compared to other technologies.

Some of the technologies currently in development for the transferprocess include pick & place, laser lift-off (LLO), and self-assembly.Among these technologies, the self-assembly approach is a method thatallows semiconductor light-emitting diodes to find their positions ontheir own in a fluid, which is most advantageous in realizinglarge-screen display devices.

Recently, U.S. Pat. No. 9,825,202 disclosed a microLED structuresuitable for self-assembly, but there is not enough research beingcarried out on technologies for manufacturing displays by theself-assembly of microLEDs. In view of this, the present disclosureproposes a new manufacturing method and device for self-assemblingmicroLEDs.

SUMMARY OF THE DISCLOSURE

One aspect of the present disclosure is to provide a new manufacturingprocess that provides high reliability in large-screen displays usingmicro-sized semiconductor light-emitting diodes.

Another aspect of the present disclosure is to provide a manufacturingprocess, capable of improving transfer accuracy when self-assemblingsemiconductor light-emitting diodes onto an assembly substrate.

Still another aspect of the present disclosure is to provide amanufacturing process, which facilitates semiconductor light-emittingdiodes to be smoothly separated from an assembly substrate afterself-assembling the semiconductor light-emitting diodes, and theassembly substrate.

To achieve those aspects and other advantages of the present disclosure,the present disclosure relates to an assembly substrate used for adisplay device manufacturing method of mounting semiconductorlight-emitting diodes on the assembly substrate at preset positionsusing electric field and magnetic field. Specifically, the assemblysubstrate may include a base portion, a plurality of assembly electrodesextending in one direction and disposed on the base portion, adielectric layer stacked on the base portion to cover the assemblyelectrodes, a barrier wall formed on the base portion and having aplurality of recesses for guiding the semiconductor light-emittingdiodes to the preset positions, and a metal shielding layer formed onthe base portion, wherein the metal shielding layer overlaps the barrierwall so that an electric field formed between the assembly electrodes isshielded.

In one embodiment, the metal shielding layer may be disposed to overlapat least part of a remaining area, except for areas where the pluralityof recesses is formed, of an entire area of the barrier wall.

In one embodiment, the metal shielding layer may be formed on edges ofthe plurality of recesses.

In one embodiment, the metal shielding layer may cover gaps between theassembly electrodes.

In one embodiment, the metal shielding layer may be disposed between thebarrier wall and the dielectric layer.

In one embodiment, the barrier wall may include a first barrier wallformed on the dielectric layer, and a second barrier wall formed on thefirst barrier wall, and the metal shielding layer may be disposedbetween the first barrier wall and the second barrier wall.

In one embodiment, the barrier wall may include a first surface incontact with the dielectric layer, and a second surface opposite to thefirst surface, and the metal shielding layer may be disposed to coverthe second surface.

In one embodiment, a sum of a thickness of the barrier wall and athickness of the metal shielding layer in a direction perpendicular tothe assembly substrate may be smaller than a thickness of thesemiconductor light-emitting diode mounted in the recess.

In one embodiment, at least one type of insulating material may bedisposed between the metal shielding layer and the assembly electrodesso that the insulated state between the metal shielding layer and theassembly electrodes is maintained.

According to another aspect of the present disclosure, there is provideda method of manufacturing a semiconductor light-emitting diode, themethod including feeding an assembly substrate having a plurality ofassembly electrodes to an assembly site and putting semiconductorlight-emitting diodes into a fluid chamber, applying a magnetic force tothe semiconductor light-emitting diodes so that the semiconductorlight-emitting diodes move in one direction within the fluid chamber,applying a voltage to each of the assembly electrodes such that thesemiconductor light-emitting diodes are guided onto preset positions byan electric field formed between the assembly electrodes while thesemiconductor light-emitting diodes move along the one direction, andtransferring the semiconductor light-emitting diodes placed on theassembly substrate onto a wiring substrate. The assembly substrate maybe provided with a metal shielding layer disposed thereon for shieldingan electric field so as to prevent the electric field from being formedin areas except for the preset positions.

In one embodiment, the transferring the semiconductor light-emittingdiodes, placed on the assembly substrate, to the wiring substrate mayinclude pressing the transfer substrate onto the assembly substrate totransfer the semiconductor light-emitting diodes from the assemblysubstrate to the transfer substrate, and pressing the transfer substrateonto the wiring substrate to transfer the semiconductor light-emittingdiodes from the transfer substrate to the wiring substrate.

In one embodiment, the transfer substrate may include a plurality ofprotrusions, and the transferring the semiconductor light-emittingdiodes from the assembly substrate to the transfer substrate may beperformed after aligning the assembly substrate and the transfersubstrate so that the protrusions and the semiconductor light-emittingdiodes overlap each other.

In one embodiment, the assembly substrate may include a first assemblysubstrate on which semiconductor light-emitting diodes emitting light ofa first color are mounted, and a second assembly substrate on whichsemiconductor light-emitting diodes emitting light of a second colordifferent from the first color are mounted. The transferring thesemiconductor light-emitting diodes, placed on the assembly substrate,to the wiring substrate may include transferring the semiconductorlight-emitting diodes, placed on the first assembly substrate andemitting the light of the first color, to the wiring substrate, andtransferring the semiconductor light-emitting diodes, placed on thesecond assembly substrate and emitting the light of the second color, tothe wiring substrate.

In one embodiment, the transferring the semiconductor light-emittingdiodes, placed on the assembly substrate, to the wiring substrate mayinclude pressing the transfer substrate onto the first assemblysubstrate to transfer the semiconductor light-emitting diodes emittingthe light of the first color from the first assembly substrate to thetransfer substrate, pressing the transfer substrate onto the secondassembly substrate to transfer the semiconductor light-emitting diodesemitting the light of the second color from the second assemblysubstrate to the transfer substrate, and pressing the transfer substrateonto the wiring substrate to transfer the semiconductor light-emittingdiodes emitting the light of the first and second colors from thetransfer substrate to the wiring substrate.

In one embodiment, the transferring the semiconductor light-emittingdiodes, placed on the assembly substrate, to the wiring substrate mayinclude pressing a first transfer substrate onto the first assemblysubstrate to transfer the semiconductor light-emitting diodes emittingthe light of the first color from the first assembly substrate to thefirst transfer substrate, pressing a second transfer substrate onto thesecond assembly substrate to transfer the semiconductor light-emittingdiodes emitting the light of the second color from the second assemblysubstrate to the second transfer substrate, and pressing the first andsecond transfer substrates onto the wiring substrate to transfer thesemiconductor light-emitting diodes emitting the light of the first andsecond colors from the first and second transfer substrates to thewiring substrate.

In one embodiment, the transfer substrate may be a polydimethylsiloxane(PDMS) substrate.

With the above configuration according to the present disclosure, largenumbers of semiconductor light-emitting diodes can be assembled at atime on a display device where individual pixels are made up ofmicroLEDs.

As such, according to the present disclosure, large numbers ofsemiconductor light-emitting diodes can be pixelated on a small-sizedwafer and then transferred onto a large-area substrate. This enables themanufacture of a large-area display device at a low cost.

Moreover, according to the manufacturing method of the presentdisclosure, a low-cost, high-efficiency, and quick transfer ofsemiconductor light-emitting diodes can be done, regardless of the sizesor numbers of parts and the transfer area, by simultaneouslytransferring them in the right positions in a solution by using amagnetic field and an electric field.

Furthermore, the assembling of semiconductor light-emitting diodes by anelectric field allows for selective assembling through selectiveelectrical application without any additional equipment or processes.Also, since an assembly substrate is placed on top of a chamber, thesubstrate can be easily loaded or unloaded, and non-specific binding ofsemiconductor light-emitting diodes can be prevented.

Additionally, formation of an electric field at unnecessary positionscan be prevented by using the assembly substrate according to thepresent disclosure, thereby improving self-assembly accuracy.

Meanwhile, in the related art, there has been a problem that thethickness of the barrier wall formed on the assembly substrate wasinevitably increased in order to prevent an electric field from beingformed at unnecessary positions. If the thickness of the barrier wall isincreased, a problem may arise that the semiconductor light-emittingdiodes cannot be smoothly separated from the assembly substrate in aprocess after self-assembly. Since the assembly substrate according tothe present disclosure comes with a metal shielding layer whichcompletely shields an electric field at unnecessary positions, thethickness of the barrier wall does not need to be increased.Accordingly, the present disclosure enables the semiconductorlight-emitting diodes to be smoothly separated from the assemblysubstrate during the process after the self-assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram illustrating one embodiment of a displaydevice using semiconductor light-emitting diodes according to thepresent disclosure.

FIG. 2 is a partial enlarged view of the portion A in the display deviceof FIG. 1 .

FIG. 3 is an enlarged view of the semiconductor light-emitting diodes ofFIG. 2 .

FIG. 4 is an enlarged view illustrating another embodiment of thesemiconductor light-emitting diodes of FIG. 2 .

FIGS. 5A to 5E are conceptual diagrams for explaining a new process formanufacturing the above-described semiconductor light-emitting diodes.

FIG. 6 is a conceptual diagram illustrating an example of a device forself-assembling semiconductor light-emitting diodes according to thepresent disclosure.

FIG. 7 is a block diagram of the self-assembly device of FIG. 6 .

FIGS. 8A to 8E are conceptual diagrams illustrating a process forself-assembling semiconductor light-emitting diodes using theself-assembly device of FIG. 6 .

FIG. 9 is a conceptual diagram for explaining the semiconductorlight-emitting diodes of FIGS. 8A to 8E.

FIGS. 10A to 10C are conceptual diagrams illustrating a state in whichthe semiconductor light-emitting diodes are transferred after aself-assembling process according to the present disclosure.

FIGS. 11 to 13 are flowcharts illustrating a method for manufacturing adisplay device including semiconductor light-emitting diodes that emitred (R), green (G), and blue (B) light.

FIGS. 14 and 15 are conceptual diagrams illustrating the form of anelectric field formed between assembly electrodes.

FIGS. 16 to 18 are conceptual views illustrating an assembly substrateaccording to the present disclosure.

FIGS. 19 and 20 are conceptual views illustrating an assembly substrateaccording to the present disclosure, viewed from the top.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Description will now be given in detail according to exemplaryembodiments disclosed herein, with reference to the accompanyingdrawings. For the sake of brief description with reference to thedrawings, the same or equivalent components may be provided with thesame or similar reference numbers, and description thereof will not berepeated. In general, a suffix such as “module” and “unit” may be usedto refer to elements or components. Use of such a suffix herein ismerely intended to facilitate description of the specification, and thesuffix itself is not intended to give any special meaning or function.In describing the present disclosure, if a detailed explanation for arelated known function or construction is considered to unnecessarilydivert the gist of the present disclosure, such explanation has beenomitted but would be understood by those skilled in the art. Theaccompanying drawings are used to help easily understand the technicalidea of the present disclosure and it should be understood that the ideaof the present disclosure is not limited by the accompanying drawings.

It will be understood that when an element such as a layer, area orsubstrate is referred to as being “on” another element, it can bedirectly on the element, or one or more intervening elements may also bepresent.

A display device disclosed herein may include a portable phone, a smartphone, a laptop computer, a digital broadcast terminal, a personaldigital assistant (PDA), a portable multimedia player (PMP), anavigation, a slate PC, a tablet PC, an ultrabook, a digital TV, adigital signage, a head mounted display (HMD), a desktop computer, andthe like. However, it will be readily apparent to those skilled in theart that the configuration according to the embodiments described hereinmay also be applied to a new product type that will be developed laterif the device is a device capable of emitting light.

FIG. 1 is a conceptual diagram illustrating one embodiment of a displaydevice using semiconductor light-emitting diodes according to thepresent disclosure, FIG. 2 is a partial enlarged view of the portion Ain the display device of FIG. 1 , FIG. 3 is an enlarged view of thesemiconductor light-emitting diodes of FIG. 2 , and FIG. 4 is anenlarged view illustrating another embodiment of the semiconductorlight-emitting diodes of FIG. 2 .

According to the illustration, information processed by a controller ofa display device 100 may be output by a display module 140. A closedloop-shaped case 101 that runs around the edge of the display module mayform the bezel of the display device.

The display module 140 comes with a panel 141 that displays an image,and the panel 141 may come with micro-sized semiconductor light-emittingdiodes 150 and a wiring substrate 110 where the semiconductorlight-emitting diodes 150 are mounted.

The wiring substrate 110 may be formed with wiring lines, which can beconnected to n-type electrodes 152 and p-type electrodes 156 of thesemiconductor light-emitting diodes 150. As such, the semiconductorlight-emitting diodes 150 may be provided on the wiring substrate 110 asindividual pixels that emit light on their own.

The image displayed on the panel 141 is visual information, which isrendered by controlling the light emission of unit pixels (sub-pixels)arranged in a matrix independently through the wiring lines.

The present disclosure takes microLEDs (light-emitting diodes) as anexample of the semiconductor light-emitting diodes 150 which convertcurrent into light. The microLEDs may be light-emitting diodes that aresmall in size—less than 100 microns. The semiconductor light-emittingdiodes 150 have light-emitting regions of red, green, and blue, and unitpixels can produce light through combinations of these colors. That is,the unit pixels are the smallest units for producing one color. Eachunit pixel may contain at least three microLEDs.

More specifically, referring to FIG. 3 , the semiconductorlight-emitting diode 150 may have a vertical structure.

For example, the semiconductor light-emitting diodes 150 may beimplemented as high-power light-emitting diodes that are composed mostlyof gallium nitride (GaN), with some indium (In) and/or aluminum (Al)added to it, and emit light of various colors.

Such a vertical semiconductor light-emitting diode comprises a p-typeelectrode 156, a p-type semiconductor layer 155 formed on the p-typesemiconductor layer 156, an active layer 154 formed on the p-typesemiconductor layer 155, an n-type semiconductor layer 153 formed on theactive layer 154, and an n-type electrode 152 formed on the n-typesemiconductor layer 153. In this case, the p-type electrode 156 at thebottom may be electrically connected to a p electrode of the wiringsubstrate, and the n-type electrode 152 at the top may be electricallyconnected to an n electrode above the semiconductor light-emittingdiode. The electrodes may be disposed in the upward/downward directionin the vertical semiconductor light-emitting diode 150, therebyproviding a great advantage capable of reducing the chip size.

In another example, referring to FIG. 4 , the semiconductorlight-emitting diodes may be flip chip-type light-emitting diodes.

As an example of such a flip chip-type light-emitting diode, thesemiconductor light-emitting diode 250 comprises a p-type electrode 256,a p-type semiconductor layer 255 formed on the p-type semiconductorlayer 256, an active layer 254 formed on the p-type semiconductor layer255, an n-type semiconductor layer 253 formed on the active layer 254,and an n-type electrode 252 vertically separated from the p-typeelectrode 256, on the n-type semiconductor layer 253. In this case, boththe p-type electrode 256 and the n-type electrode 252 may beelectrically connected to a p electrode and n electrode of the wiringsubstrate, below the semiconductor light-emitting diode.

The vertical semiconductor light-emitting diode and a horizontallight-emitting diode each may be used as a green semiconductorlight-emitting diode, blue semiconductor light-emitting diode, or redsemiconductor light-emitting diode. The green semiconductorlight-emitting diode and the blue semiconductor light-emitting diode maybe implemented as high-power light-emitting diodes that are composedmostly of gallium nitride (GaN), with some indium (In) and/or aluminum(Al) added to it, and emit green and blue light, respectively. As anexample of such high-power light-emitting diodes, the semiconductorlight-emitting diodes may be composed of gallium nitride thin filmswhich are formed of various layers of n-Gan, p-GaN, AlGaN, InGaN, etc.More specifically, the p-type semiconductor layer may be P-type GaN, andthe n-type semiconductor layer may be N-type GaN. However, for the redsemiconductor light-emitting diodes, the p-type semiconductor layer maybe P-type GaAs, and the n-type semiconductor layer may be N-type GaAs.

Moreover, the p-type semiconductor layer may be P-type GaN doped with Mgon the p electrode, and the n-type semiconductor layer may be N-type GaNdoped with Si on the n electrode. In this case, the above-describedsemiconductor light-emitting diodes may come without the active layer.

Meanwhile, referring to FIGS. 1 to 4 , because of the very small size ofthe light-emitting diodes, self-emissive, high-definition unit pixelsmay be arranged on the display panel, and therefore the display devicecan deliver high picture quality.

In the above-explained display device using semiconductor light-emittingdiodes according to the present disclosure, semiconductor light-emittingdiodes are grown on a wafer, formed through mesa and isolation, and usedas individual pixels. In this case, the micro-sized semiconductorlight-emitting diodes 150 should be transferred onto a wafer, at presetpositions on a substrate of the display panel. One of the transfertechnologies available is pick and place, but it has a low success rateand requires a lot of time. In another example, a number of diodes maybe transferred at a time by using a stamp or roll, which, however, isnot suitable for large-screen displays because of limited yields. Thepresent disclosure suggests a new method and device for manufacturing adisplay device that can solve these problems.

To this end, the new method for manufacturing a display device will bedescribed first below. FIGS. 5A to 5E are conceptual diagrams forexplaining a new process for manufacturing the above-describedsemiconductor light-emitting diodes.

In this specification, a display device using passive matrix (PM)semiconductor light-emitting diodes will be illustrated. It should benoted that the illustration given below also applies to active matrix(AM) semiconductor light-emitting diodes. Also, although theillustration will be given of how horizontal semiconductorlight-emitting diodes are self-assembled, it may also apply toself-assembling of vertical semiconductor light-emitting diodes.

First of all, according to the manufacturing method, a first conductivesemiconductor layer 153, an active layer 154, and a second conductivesemiconductor layer 155 are grown on a growth substrate 159 (FIG. 5A).

Once the first conductive semiconductor layer 153 is grown, then theactive layer 154 is grown on the first conductive semiconductor layer153, and then the second conductive semiconductor layer 155 is grown onthe active layer 154. By sequentially growing the first conductivesemiconductor layer 153, active layer 154, and second conductivesemiconductor layer 155, the first conductive semiconductor layer 153,active layer 154, and second conductive semiconductor layer 155 form astack structure as shown in FIG. 5A.

In this case, the first conductive semiconductor layer 153 may be ap-type semiconductor layer, and the second conductive semiconductorlayer 155 may be an n-type semiconductor layer. However, the presentdisclosure is not necessarily limited to this, and the first conductivetype may be n-type and the second conductive type may be p-type.

Moreover, although this exemplary embodiment is illustrated by assumingthe presence of the active layer, the active layer may be omitted ifnecessary, as stated above. In an example, the p-type semiconductorlayer may be P-type GaN doped with Mg, and the n-type semiconductorlayer may be N-type GaN doped with Si on the n electrode.

The growth substrate 159 (wafer) may be formed of, but not limited to,light-transmissive material—for example, at least one among sapphire(Al₂O₃), GaN, ZnO, and AlO. Also, the growth substrate 159 may be madefrom a material suitable for growing semiconductor materials or carrierwafer. The growth substrate 159 may be formed of a high thermalconducting material, and may be a conductive substrate or insulatingsubstrate—for example, at least one among SiC, Si, GaAs, GaP, InP, andGa2O3 substrates which have higher thermal conductivity than sapphire(Al2O3) substrates.

Next, a plurality of semiconductor light-emitting diodes is formed byremoving at least part of the first conductive semiconductor layer 153,active layer 154, and second conductive semiconductor layer 155 (FIG.5B).

More specifically, isolation is performed so that the light-emittingdiodes form a light-emitting diode array. That is, a plurality ofsemiconductor light-emitting diodes is formed by vertically etching thefirst conductive semiconductor layer 153, active layer 154, and secondconductive semiconductor layer 155.

In the case of horizontal semiconductor light-emitting diodes, a mesaprocess may be performed which exposes the first conductivesemiconductor layer 153 to the outside by vertically removing part ofthe active layer 154 and second conductive layer 155, and then isolationmay be performed which forms an array of semiconductor light-emittingdiodes by etching the first conductive semiconductor layer 153.

Next, a second conductive electrode 156 (or p-type electrode) is formedon one surface of the second conductive semiconductor layer 155 (FIG.5C). The second conductive electrode 156 may be formed by a depositionmethod such as sputtering, but the present disclosure is not necessarilylimited to this. In a case where the first conductive semiconductorlayer and the second conductive semiconductor layer are an n-typesemiconductor layer and a p-type semiconductor layer, respectively, thesecond conductive electrode 156 may serve as an n-type electrode.

Next, the growth substrate 159 is removed, thus leaving a plurality ofsemiconductor light-emitting diodes. For example, the growth substrate159 may be removed using laser lift-off (LLO) or chemical lift-off (CLO)(FIG. 5D).

Afterwards, the step of mounting the semiconductor light-emitting didoes150 on a substrate in a chamber filled with a fluid is performed (FIG.5E).

For example, the semiconductor light-emitting diodes 150 and thesubstrate are put into the chamber filled with a fluid, and thesemiconductor light-emitting diodes are self-assembled onto thesubstrate 161 using fluidity, gravity, surface tension, etc. In thiscase, the substrate may be an assembly substrate 161.

In another example, a wiring substrate, instead of the assemblysubstrate 161, may be put into a fluid chamber, and the semiconductorlight-emitting diodes 150 may be mounted directly onto the wiringsubstrate. In this case, the substrate may be a wiring substrate. Forconvenience of explanation, the present disclosure is illustrated withan example in which the semiconductor light-emitting diodes 150 aremounted onto the assembly substrate 161.

To facilitate the mounting of the semiconductor light-emitting diodes150 onto the assembly substrate 161, cells (not shown) into which thesemiconductor light-emitting diodes 150 are fitted may be provided onthe assembly substrate 161. Specifically, cells where the semiconductorlight-emitting diodes 150 are mounted are formed on the assemblysubstrate 161, at positions where the semiconductor light-emittingdiodes 150 are aligned with wiring electrodes. The semiconductorlight-emitting diodes 150 are assembled to the cells as they move withinthe fluid.

After arraying the semiconductor light-emitting didoes on the assemblysubstrate 161, the semiconductor light-emitting diodes may betransferred to the wiring substrate from the assembly substrate 161,thereby enabling a large-area transfer across a large area. Thus, theassembly substrate 161 may be referred to as a temporary substrate.

Meanwhile, the above-explained self-assembly method requires a highertransfer yield so that it can be applied to the manufacture oflarge-screen displays. The present disclosure proposes a method anddevice that minimizes the effects of gravity or friction and avoidsnon-specific binding, in order to increase the transfer yield.

In this case, in the display device according to the present disclosure,a magnetic material is placed on the semiconductor light-emitting diodesso that the semiconductor light-emitting diodes are moved by magneticforce, and the semiconductor light-emitting diodes are mounted at presetpositions by an electric field while in the process of being moved. Thistransfer method and device will be described in more details below withreference to the accompanying drawings.

FIG. 6 is a conceptual diagram showing an example of a device forself-assembling semiconductor light-emitting diodes according to thepresent disclosure, and FIG. 7 is a block diagram of the self-assemblydevice of FIG. 6 . FIGS. 8A to 8E are conceptual diagrams showing aprocess for self-assembling semiconductor light-emitting diodes usingthe self-assembly device of FIG. 6 . FIG. 9 is a conceptual diagram forexplaining the semiconductor light-emitting diodes of FIGS. 8A to 8E.

Referring to FIGS. 6 and 7 , the self-assembly device 160 of the presentdisclosure may comprise a fluid chamber 162, magnets 163, and a positioncontroller 164.

The fluid chamber 162 is equipped with space for a plurality ofsemiconductor light-emitting diodes. The space may be filled with afluid, and the fluid may be an assembly solution, which includes wateror the like. Thus, the fluid chamber 162 may be a water tank andconfigured as open-type. However, the present disclosure is not limitedto this, and the fluid chamber 162 may be a closed-type chamber thatcomes with a closed space.

A substrate 161 may be placed in the fluid chamber 162 so that anassembly surface where the semiconductor light-emitting diodes 150 areassembled faces downwards. For example, the substrate 161 is fed to anassembly site by a feed unit, and the feed unit may come with a stage165 where the substrate is mounted. The position of the stage 165 may beadjusted by the controller, whereby the substrate 161 may be fed to theassembly site.

In this instance, the assembly surface of the substrate 161 at theassembly site faces the bottom of the fluid chamber 162. As shown in thedrawings, the assembly surface of the substrate 161 is placed in such away as to be soaked with the fluid in the fluid chamber 162. Thus, thesemiconductor light-emitting diodes 150 in the fluid are moved to theassembly surface.

The substrate 161 is an assembly substrate where an electric field canbe formed, and may comprise a base portion 161 a, a dielectric layer 161b, and a plurality of electrodes 161 c.

The base portion 161 a is made of insulating material, and theelectrodes 161 c may be thin-film or thick-film bi-planar electrodesthat are patterned on one surface of the base portion 161 a. Theelectrodes 161 c may be formed of a stack of Ti/Cu/Ti, Ag paste, ITO,etc.

The dielectric layer 161 b may be made of inorganic material such asSiO2, SiNx, SiON, Al2O3, TiO2, HfO2, etc. Alternatively, the dielectriclayer 161 b may be an organic insulator and composed of a single layeror multi-layers. The thickness of the dielectric layer 161 b may rangefrom several tens of nm to several μm.

Further, the substrate 161 according to the present disclosure comprisesa plurality of cells 161 d that are separated by barrier walls 161 e.The cells 161 d may be sequentially arranged in one direction and madeof polymer material. Also, the barrier walls 161 e forming the cells 161d may be shared with neighboring cells 161 d. The barrier walls 161 emay protrude from the base portion 161 a, and the cells 161 d may besequentially arranged in one direction along the barrier walls 161 e.More specifically, the cells 161 d may be sequentially arranged incolumn and row directions and have a matrix structure.

As shown in the drawings, the cells 161 d may have recesses forcontaining the semiconductor light-emitting diodes 150, and the recessesmay be spaces defined by the barrier walls 161 e. The recesses may havea shape identical or similar to the shape of the semiconductorlight-emitting diodes. For example, if the semiconductor light-emittingdiodes are rectangular, the recesses may be rectangular too. Moreover,although not shown, the recesses formed in the cells may be circular ifthe semiconductor light-emitting diodes are circular. Further, each cellis configured to contain one semiconductor light-emitting diode. Thatis, one cell contains one semiconductor light-emitting diode.

Meanwhile, the plurality of electrodes 161 c have a plurality ofelectrode lines that are placed at the bottom of the cells 161 d, andthe electrode lines may be configured to extend to neighboring cells.

The electrodes 161 c are placed on the undersides of the cells 161 d,and different polarities may be applied to create an electric fieldwithin the cells 161 d. To form an electric field, the dielectric layer161 b may form the bottom of the cells 161 d while covering theelectrodes 161 c. With this structure, when different polarities areapplied to a pair of electrodes 161 c on the underside of each cell 161d, an electric field is formed and the semiconductor light-emittingdiodes can be inserted into the cells 161 d by the electric field.

The electrodes of the substrate 161 at the assembly site areelectrically connected to a power supply 171. The power supply 171performs the function of generating an electric field by applying powerto the electrodes.

As shown in the drawings, the self-assembly device may have magnets 163for applying magnetic force to the semiconductor light-emitting diodes.The magnets 163 are placed at a distance from the fluid chamber 162 andapply a magnetic force to the semiconductor light-emitting diodes 150.The magnets 163 may be placed to face the opposite side of the assemblysurface of the substrate 161, and the positions of the magnets 163 arecontrolled by the position controller 164 connected to the magnets 163.

The semiconductor light-emitting diodes 1050 may have a magneticmaterial so that they are moved within the fluid by a magnetic field.

Referring to FIG. 9 , a semiconductor light-emitting diode having amagnetic material may comprise a first conductive electrode 1052, asecond conductive electrode 1056, a first conductive semiconductor layer1053 where the first conductive electrode 1052 is placed, a secondconductive semiconductor layer 1055 which overlaps the first conductivesemiconductor layer 1052 and where the second conductive layer 1056 isplaced, and an active layer 1054 placed between the first and secondconductive semiconductor layers 1053 and 1055.

Here, the first conductive may refer to p-type, and the secondconductive type may refer to n-type, or vice versa. As statedpreviously, the semiconductor light-emitting diode may be formed withoutthe active layer.

Meanwhile, in the present disclosure, the first conductive electrode1052 may be formed after the semiconductor light-emitting diode isassembled onto the wiring substrate by the self-assembling of thesemiconductor light-emitting diode. Further, in the present disclosure,the second conductive electrode 1056 may comprise a magnetic material.The magnetic material may refer a magnetic metal. The magnetic materialmay be Ni, SmCo, etc. In another example, the magnetic material mayinclude at least one among Gd-based, La-based, and Mn-based materials.

The magnetic material may be provided in the form of particles on thesecond conductive electrode 1056. Alternatively, one layer of aconductive electrode comprising a magnetic material may be composed ofthe magnetic material. An example of this is the second conductiveelectrode 1056 of the semiconductor light-emitting diode 1050 whichcomprises a first layer 1056 a and a second layer 1056 b, as shown inFIG. 9 . Here, the first layer 1056 a may comprise a magnetic material,and the second layer 1056 b may comprise a metal material other than themagnetic material.

As shown in the drawing, in this example, the first layer 1056 acomprising the magnetic material may be placed in contact with thesecond conductive semiconductor layer 1055. In this case, the firstlayer 1056 a is placed between the second layer 1056 b and the secondconductive semiconductor layer 1055. The second layer 1056 b may be acontact metal that is connected to the wiring electrode on the wiringsubstrate. However, the present disclosure is not necessarily limited tothis, and the magnetic material may be placed on one surface of thefirst conductive semiconductor layer.

Referring again to FIGS. 6 and 7 , more specifically, on top of thefluid chamber of the self-assembly device, a magnet handler capable ofautomatically or manually moving the magnets 163 on the x, y, and z axesor a motor capable of rotating the magnets 163 may be provided. Themagnet handler and motor may constitute the position controller 164. Assuch, the magnets 163 may rotate in a horizontal, clockwise, orcounterclockwise direction to the substrate 161.

Meanwhile, the fluid chamber 162 may be formed with a light-transmissivebottom plate 166, and the semiconductor light-emitting diodes may beplaced between the bottom plate 166 and the substrate 161. An imagesensor 167 may be placed opposite the bottom plate 166 so as to monitorthe inside of the fluid chamber 162 through the bottom plate 166. Theimage sensor 167 may be controlled by a controller 172, and may comewith an inverted-type lens, CCD, etc. so as to observe the assemblysurface of the substrate 161.

The above-explained self-assembly device is configured to use a magneticfield and an electric field in combination. With this, the semiconductorlight-emitting diodes are mounted at preset positions on the substrateby an electric field while in the process of being moved by changes inthe positions of the magnets. Below, the assembly process using theabove-explained self-assembly device will be described in more details.

First of all, a plurality of semiconductor light-emitting diodes 1050having a magnetic material may be formed through the process explainedwith reference to FIGS. 5A to 5C. In this case, the magnetic materialmay be deposited onto the semiconductor light-emitting didoes in theprocess of forming the second conductive electrode of FIG. 5C.

Next, the substrate 161 is fed to an assembly site, and thesemiconductor light-emitting diodes 1050 are put into the fluid chamber162 (FIG. 8A).

As described above, the assembly site on the substrate 161 may be aposition at which the substrate 161 is placed in the fluid chamber 162in such a way that an assembly surface where the semiconductorlight-emitting diodes 150 are assembled faces downwards.

In this case, some of the semiconductor light-emitting diodes 1050 maysink to the bottom of the fluid chamber 162 and some of them may floatin the fluid. If the fluid chamber 162 comes with a light-transmissivebottom plate 166, some of the semiconductor light-emitting diodes 1050may sink to the bottom plate 166.

Next, a magnetic force is applied to the semiconductor light-emittingdiodes 1050 so that the semiconductor light-emitting diodes 1050 in thefluid chamber 162 come up to the surface (FIG. 8B).

When the magnets 163 of the self-assembly device move to the oppositeside of the assembly surface of the substrate 161 from their originalpositions, the semiconductor light-emitting diodes 1050 float in thefluid towards the substrate 161. The original positions may refer topositions at which the magnets 163 are outside the fluid chamber 162. Inanother example, the magnets 163 may be composed of electromagnets. Inthis case, an initial magnetic force is generated by supplyingelectricity to the electromagnets.

Meanwhile, in this embodiment, the spacing between the assembly surfaceof the substrate 161 and the semiconductor light-emitting diodes 1050may be controlled by adjusting the strength of the magnetic force. Forexample, the spacing is controlled by using the weight, buoyancy, andmagnetic force of the semiconductor light-emitting diodes 1050. Thespacing may be several millimeters to several tens of micrometers fromthe outermost part of the substrate 161.

Next, a magnetic force is applied to the semiconductor light-emittingdiodes 1050 so that the semiconductor light-emitting diodes 1050 move inone direction within the fluid chamber 162. For example, the magnets 163may move in a horizontal, clockwise, or counterclockwise direction tothe substrate 161 (FIG. 8C). In this case, the semiconductorlight-emitting diodes 1050 are moved horizontally to the substrate 161by the magnetic force, spaced apart from the substrate 161.

Next, the semiconductor light-emitting diodes 1050 are guided to presetpositions on the substrate 161 by applying an electric field so that thesemiconductor light-emitting diodes 1050 are mounted at the presetpositions while in the process of being moved (FIG. 8C). For example,the semiconductor light-emitting diodes 1050 are moved vertically to thesubstrate 161 by the electric field and mounted at preset positions onthe substrate 161, while being moved horizontally to the substrate 161.

More specifically, an electric field is generated by supplying power tobi-planar electrodes on the substrate 161, and the semiconductorlight-emitting diodes 1050 are guided to the preset positions andassembled only there by the electric field. That is, the semiconductorlight-emitting diodes 1050 are self-assembled at an assembly site on thesubstrate 161 by a selectively generated electric field. To this end,the substrate 161 may be formed with cells into which the semiconductorlight-emitting diodes 1050 are fitted.

Afterwards, the unloading of the substrate 161 is performed, therebycompleting the assembly process. In a case where the substrate 161 is anassembly substrate, an array of semiconductor light-emitting diodes maybe transferred onto a wiring substrate to carry out a subsequent processfor realizing the display device, as described previously.

Meanwhile, after the semiconductor light-emitting diodes 1050 are guidedto the preset positions, the magnets 163 may be moved in a direction inwhich they get farther away from the substrate 161, so that thesemiconductor light-emitting diodes 1050 remaining in the fluid chamber162 fall to the bottom of the fluid chamber 162 (FIG. 8D). In anotherexample, if power supply is stopped in a case where the magnets 163 areelectromagnets, the semiconductor light-emitting diodes 1050 remainingin the fluid chamber 162 fall to the bottom of the fluid chamber 162.

Thereafter, the semiconductor light-emitting diodes 1050 on the bottomof the fluid chamber 162 may be collected, and the collectedsemiconductor light-emitting diodes 1050 may be re-used.

In the above-explained self-assembly device and method, parts distantfrom one another are concentrated near a preset assembly site by using amagnetic field in order to increase assembly yields in a fluidicassembly, and the parts are selectively assembled only at the assemblysite by applying an electric field to the assembly site. In this case,the assembly substrate is positioned on top of a water tank, with itsassembly surface facing downward, thus minimizing the effect of gravityfrom the weights of the parts and avoiding non-specific binding andeliminating defects. That is, the assembly substrate is placed on thetop to increase transfer yields, thus minimizing the effect of gravityor friction and avoiding non-specific binding.

As seen from above, with the above configuration according to thepresent disclosure, large numbers of semiconductor light-emitting diodescan be assembled at a time on a display device where individual pixelsare made up of semiconductor light-emitting diodes.

As such, according to the present disclosure, large numbers ofsemiconductor light-emitting diodes can be pixelated on a small-sizedwafer and then transferred onto a large-area substrate. This enables themanufacture of a large-area display device at a low cost.

Meanwhile, the present disclosure provides a structure and method of anassembly substrate for increasing the yields of the self-assemblyprocess and the process yields after the self-assembly. The presentdisclosure is limited to a case where the substrate 161 is used as anassembly substrate. That is, the assemble substrate to be describedlater is not used as the wiring substrate of the display device.Hereinafter, the substrate 161 is referred to as an assembly substrate161.

The present disclosure improves the process yields in two respects.First, the present disclosure prevents semiconductor light-emittingdiodes from being mounted on undesired positions due to an electricfield strongly formed at the undesired positions. Second, the presentdisclosure prevents the semiconductor light-emitting diodes fromremaining on the assemble substrate when transferring the semiconductorlight-emitting diodes mounted on the assemble substrate to anothersubstrate.

The above-mentioned objectives are not individually achieved bydifferent components. The above-described two objectives can be achievedby organic coupling of components to be described later and the assemblysubstrate 161 described above.

Before describing the present disclosure in detail, a post-process formanufacturing a display device after self-assembling will be described.

FIGS. 10A to 10C are conceptual diagrams illustrating a state in whichthe semiconductor light emitting devices are transferred after aself-assembling process according to the present disclosure.

When the self-assembly process described with reference to FIGS. 8A to8E is completed, the semiconductor light-emitting diodes are mounted onthe assembly substrate 161 at preset positions. The semiconductorlight-emitting diodes mounted on the assembly substrate 161 aretransferred at least once to another substrate. This specificationillustrates one embodiment in which the semiconductor light-emittingdiodes mounted on the assembly substrate 161 are transferred twice, butthe present disclosure is not limited thereto. The semiconductorlight-emitting diodes mounted on the assembly substrate 161 may betransferred to another substrate once or three times or more.

On the other hand, immediately after the self-assembly process iscompleted, the assembly surface of the assembly substrate 161 facesdownwards (or the gravity direction). For the process after theself-assembly, the assembly substrate 161 may be turned by 180 degreeswith the semiconductor light-emitting diodes mounted thereon. In thisprocess, there is a risk that the semiconductor light-emitting diodesare likely to be separated from the assembly substrate 161. Therefore, avoltage must be applied to the plurality of electrodes 161 c(hereinafter, referred to as assembly electrodes) while the assemblysubstrate 161 is turned. An electric field formed between the assemblyelectrodes prevents the semiconductor light-emitting diodes from beingseparated from the assembly substrate 161 while the assembly substrate161 is turned.

When the assembly substrate 161 is turned by 180 degrees after theself-assembly process, a shape as shown in FIG. 10A is made.Specifically, as shown in FIG. 10A, the assembly surface of the assemblysubstrate 161 is in a state of facing upwards (or the opposite directionto gravity). In this state, a transfer substrate 400 is aligned abovethe assembly substrate 161.

The transfer substrate 400 is a substrate for separating thesemiconductor light-emitting diodes placed on the assembly substrate 161and transferring them to the wiring substrate. The transfer substrate400 may be formed of PDMS (polydimethylsiloxane). Accordingly, thetransfer substrate 400 may be referred to as a PDMS substrate.

The transfer substrate 400 is aligned above the assembly substrate 161and then pressed onto the assembly substrate 161. When the transfersubstrate 400 is fed above the assembly substrate 161, the semiconductorlight-emitting diodes 350 mounted on the assembly substrate 161 aretransferred to the transfer substrate 400 by the adhesive force of thetransfer substrate 400.

To this end, surface energy between the semiconductor light-emittingdiodes 350 and the transfer substrate 400 should be higher than surfaceenergy between the semiconductor light-emitting diodes 350 and thedielectric layer 161 b. When there is a greater difference between thesurface energy between the semiconductor light-emitting diodes 350 andthe transfer substrate 400 and the surface energy between thesemiconductor light-emitting diodes 350 and the dielectric layer 161 b,the probability that the semiconductor light-emitting diodes 350 areseparated from the assembly substrate 161 is more increased. Therefore,it is preferable that the difference between the two surface energies isgreat.

Meanwhile, the transfer substrate 40 may include a plurality ofprotrusions 410 that allow pressure applied by the transfer substrate400 to be concentrated on the semiconductor light-emitting diodes 350when pressing the transfer substrate 400 onto the assembly substrate161. The protrusions 410 may be formed at the same interval as thesemiconductor light-emitting diodes mounted on the assembly substrate161. When the transfer substrate 400 is pressed onto the assemblysubstrate 161 after the protrusions 410 are aligned to overlap thesemiconductor light-emitting diodes 350, the pressure applied by thetransfer substrate 400 can be concentrated only on the semiconductorlight-emitting diodes 350. Thus, the present disclosure increases theprobability that the semiconductor light-emitting diodes are separatedfrom the assembly substrate 161.

Meanwhile, in a state where the semiconductor light-emitting diodes aremounted on the assembly substrate 161, parts of the semiconductorlight-emitting diodes are preferably exposed to the outside of therecesses. If the semiconductor light-emitting diodes 350 are not exposedto the outside of the recesses, the pressure applied by the transfersubstrate 400 is not concentrated on the semiconductor light-emittingdiodes 350, which may lower the probability that the semiconductorlight-emitting diodes 350 are separated from the assembly substrate 161.

Lastly, referring to FIG. 10C, the step of pressing the transfersubstrate 400 onto the wiring substrate 500 and transferring thesemiconductor light-emitting diodes 350 from the transfer substrate 400to the wiring substrate 500 is carried out. At this time, the wiringsubstrate 500 may be provided with protrusions 510. The transfersubstrate 400 and the wiring substrate 500 are aligned so that thesemiconductor light-emitting diodes 350 disposed on the transfersubstrate 400 overlap the protrusions 510. Thereafter, when the transfersubstrate 400 is pressed onto the wiring substrate 500, the probabilitythat the semiconductor light-emitting diodes 350 are separated from thetransfer substrate 400 may increase due to the protrusions 510.

On the other hand, in order for the semiconductor light-emitting diodes350 disposed on the transfer substrate 400 to be transferred to thewiring substrate 500, surface energy between the semiconductorlight-emitting diodes 350 and the wiring substrate 500 should be higherthan surface energy between the semiconductor light-emitting diodes 350and the transfer substrate 400. When there is a greater differencebetween the surface energy between the semiconductor light-emittingdiodes 350 and the wiring substrate 500 and the surface energy betweenthe semiconductor light-emitting diodes 350 and the transfer substrate400, the probability that the semiconductor light-emitting diodes 350are separated from the transfer substrate 400 is more increased.Therefore, it is preferable that the difference between the two surfaceenergies is great.

After all the semiconductor light-emitting diodes 350 mounted on thetransfer substrate 400 are transferred onto the wiring substrate 500,the step of establishing electrical connection between the semiconductorlight-emitting diodes 350 and wiring electrodes provided on the wiringsubstrate may be performed. The structure of the wiring electrodes andthe method of establishing the electrical connection may vary dependingon the type of the semiconductor light-emitting diodes 350.

Although not shown, an anisotropic conductive film may be disposed onthe wiring substrate 500. In this case, the electrical connection can beestablished between the semiconductor light-emitting diodes 350 and thewiring electrodes formed on the wiring substrate 500, simply by pressingthe transfer substrate 400 onto the wiring substrate 500.

On the other hand, when manufacturing a display device includingsemiconductor light-emitting diodes emitting light of different colors,the method described in FIGS. 10A to 10C can be implemented in variousways. Hereinafter, a method for manufacturing a display device includingsemiconductor light-emitting diodes that emit red (R), green (G), andblue (B) light will be described.

FIGS. 11 to 13 are flowcharts illustrating a method for manufacturing adisplay device including semiconductor light-emitting diodes that emitred (R), green (G), and blue (B) light.

Semiconductor light-emitting diodes emitting light of different colorsmay be individually assembled to different assembly substrates.Specifically, the assembly substrate 161 may include a first assemblysubstrate on which semiconductor light-emitting diodes emitting light ofa first color are mounted, a second assembly substrate on whichsemiconductor light-emitting diodes emitting light of a second colordifferent from the first color are mounted, and a third assemblysubstrate on which semiconductor light-emitting diodes emitting light ofa third color different from the first color and the second color aremounted. Different types of semiconductor light-emitting diodes areassembled to assembly substrates, respectively, according to the methoddescribed in FIGS. 8A to 8E. For example, semiconductor light-emittingdiodes emitting red (R), green (G), and blue (B) light may be assembledto the first to third assemble substrates, respectively.

Referring to FIG. 11 , a RED chip, a GREEN chip, and a BLUE chip may beassembled respectively to first to third assembly substrates REDTEMPLATE, GREEN TEMPLATE, and BLUE TEMPLATE. In this state, the REDchip, GREEN chip and BLUE chip may be transferred to the wiringsubstrate by different transfer substrates, respectively.

Specifically, the step of transferring the semiconductor light-emittingdiodes, which are mounted on the assembly substrate, to the wiringsubstrate may include pressing a first transfer substrate (stamp R) ontothe first assembly substrate RED TEMPLATE to transfer the semiconductorlight-emitting diodes (RED chip) emitting the light of the first colorfrom the first assembly substrate RED TEMPLATE to the first transfersubstrate (stamp R), pressing a second transfer substrate (stamp G) ontothe second assembly substrate GREEN TEMPLATE to transfer thesemiconductor light-emitting diodes (GREEN chip) emitting the light ofthe second color from the second assembly substrate GREEN TEMPLATE tothe second transfer substrate (stamp G), and pressing a third transfersubstrate (stamp B) onto the third assembly substrate BLUE TEMPLATE totransfer the semiconductor light-emitting diodes (BLUE chip) emittingthe light of the third color from the third assembly substrate BLUETEMPLATE to the third transfer substrate (stamp B).

Thereafter, the step of pressing the respective first to third transfersubstrates onto the wiring substrate to transfer the semiconductorlight-emitting diodes emitting the light of the first to third colorsfrom the first to third transfer substrates to the wiring substrate,respectively.

According to the manufacturing method according to FIG. 11 , three typesof assembly substrates and three types of transfer substrates arerequired to manufacture a display device including a RED chip, a GREENchip, and a BLUE chip.

On the contrary, referring to FIG. 12 , the RED chip, the GREEN chip,and the BLUE chip may be assembled to the first to third assemblysubstrates RED TEMPLATE, GREEN TEMPLATE, and BLUE TEMPLATE,respectively. In this state, the RED chip, GREEN chip and BLUE chip maybe transferred to the wiring substrate by the same transfer substrate.

Specifically, the step of transferring the semiconductor light-emittingdiodes, which are mounted on the assembly substrates, to the wiringsubstrate may include pressing a transfer substrate (RGB-integratedstamp) onto the first assembly substrate RED TEMPLATE to transfer thesemiconductor light-emitting diodes (RED chip) emitting the light of thefirst color from the first assembly substrate RED TEMPLATE to thetransfer substrate (RGB-integrated stamp), pressing the transfersubstrate (RGB-integrated stamp) onto the second assembly substrateGREEN TEMPLATE to transfer the semiconductor light-emitting diodes(GREEN chip) emitting the light of the second color from the secondassembly substrate GREEN TEMPLATE to the transfer substrate(RGB-integrated stamp), and pressing the transfer substrate(RGB-integrated stamp) onto the third assembly substrate BLUE TEMPLATEto transfer the semiconductor light-emitting diodes (BLUE chip) emittingthe light of the third color from the third assembly substrate BLUETEMPLATE to the transfer substrate (RGB-integrated stamp).

In this case, the alignment positions between the first to thirdassembly substrates and the transfer substrate may be different fromeach other. For example, when the alignment between the assemblysubstrates and the transfer substrate is completed, the relativeposition of the transfer substrate with respect to the first assemblysubstrate and the relative position of the transfer substrate withrespect to the second assembly substrate may be different from eachother. The transfer substrate may be shifted in its alignment positionby a pitch of a sub pixel every time the type of the assembly substrateis changed. In this way, when the transfer substrate is sequentiallypressed onto the first to third assembly substrates, all the three typesof chips can be transferred to the transfer substrate.

Afterwards, similar to FIG. 11 , the step of pressing the transfersubstrate onto the wiring substrate to transfer the semiconductorlight-emitting diodes emitting the light of the first to third colorsfrom the transfer substrate to the wiring substrate is carried out.

According to the manufacturing method illustrated in FIG. 12 , threetypes of assembly substrates and one type of transfer substrate arerequired to manufacture a display device including a RED chip, a GREENchip, and a BLUE chip.

Unlike FIGS. 11 and 12 , according to FIG. 13 , a RED chip, a GREENchip, and a BLUE chip may be assembled onto one assembly substrate(RGB-integrated TEMPLATE). In this state, each of the RED chip, GREENchip and BLUE chip can be transferred to the wiring substrate by thesame transfer substrate (RGB-integrated stamp).

According to the manufacturing method illustrated in FIG. 13 , one typeof assembly substrate and one type of transfer substrate are required tomanufacture a display device including a RED chip, a GREEN chip, and aBLUE chip.

As described above, when manufacturing a display device includingsemiconductor light-emitting diodes emitting light of different colors,the manufacturing method may be implemented in various ways.Hereinafter, a structure of an assembly substrate for increasing theyield of the method for manufacturing the display device described withreference to FIGS. 10A to 10C and FIGS. 11 to 13 will be described.

Prior to explanation, an electric field formed between the assemblyelectrodes when the self-assembly is carried out, which has beendescribed with reference to FIGS. 8A to 8E, will be described.

FIGS. 14 and 15 are conceptual diagrams illustrating the form of anelectric field formed between assembly electrodes.

Referring to FIG. 14 , when a voltage is applied to the assemblyelectrodes 161 c, an electric field is formed between the assemblyelectrodes 161 c. The electric field E1 becomes stronger near theassembly electrodes, and becomes weaker away from the assemblyelectrodes. The electric field may be strongly formed on surfaces of thebarrier walls adjacent to the assembly electrodes.

Specifically, referring to FIG. 15 , an area where the electric field isstrongly formed, other than the recesses formed in the barrier wall 161e, may exist. For example, the electric field may be strongly formed ona surface of an area, which covers the assembly electrode 161 c or aportion between the assembly electrodes, of the entire area of thebarrier wall 161 e. Accordingly, some of the semiconductorlight-emitting diodes may stick to the surface of the barrier wall wherethe recesses are not formed.

In order to prevent such a problem, the thickness of the barrier wall161 e has no choice but to increase. Specifically, when the thickness ofthe barrier wall 161 e is increased, the distance between the assemblyelectrodes and the barrier wall surface is increased, which may resultin reducing the phenomenon of the semiconductor light-emitting diodessticking to the barrier wall surface.

However, the increase in the thickness of the barrier wall may lower theyields of the process after the self-assembly. In an extreme case, whenthe thickness of the barrier wall is greater than the thickness of thesemiconductor light-emitting diodes that are placed in the recesses, itmakes it difficult to transfer the semiconductor light-emitting diodesplaced on the assembly substrate to another substrate.

When the process after the self-assembly illustrated in FIGS. 10A to 10Cis performed, the barrier wall interferes with the pressure applied bythe transfer substrate to the semiconductor light-emitting diodes. Asdescribed above, in order to increase the yields of the process afterthe self-assembly, it is more advantageous that the barrier wall isthinner in thickness.

In summary, the self-assembly yields can be improved as the thickness ofthe barrier wall increases, but the process yields after theself-assembly decrease. On the other hand, as the thickness of thebarrier wall decreases, the self-assembly yields may be reduced but theyields after the process of the self-assembly are improved.

The present disclosure provides a structure of an assembly substratethat can reduce the thickness of the barrier wall and improve theself-assembly yields. Hereinafter, a structure of an assembly substrateaccording to the present disclosure will be described.

FIGS. 16 to 18 are sectional views of an assembly substrate according tothe present disclosure, and FIGS. 19 to 20 are conceptual views of theassembly substrate according to the present disclosure, viewed from thetop.

The assembly substrate according to the present disclosure may include,as aforementioned, the base portion 161 a, the assembly electrodes 161c, the dielectric layer 161 b, and the barrier wall 161 e. Thedescription thereof is replaced with the foregoing description.

Meanwhile, the assembly substrate according to the present disclosureincludes a metal shielding layer formed on the base portion. The metalshielding layer is used for shielding an electric field formed betweenthe assembly electrodes 161 c.

The metal shielding layer is disposed to overlap the barrier wall so asto shield an electric field formed between the assembly electrodes 161c.

The metal shielding layer may be made of any one of Mo, Al, Ni, and Cr,or may be made of an alloy of the metals. However, the presentdisclosure is not limited thereto.

The thickness of the metal shielding layer is not particularly limited,but it is sufficient as long as the metal shielding layer can completelyshield the electric field formed between the assembly electrodes.

The metal shielding layer may be formed at various positions. In oneembodiment, referring to FIG. 16 , the metal shielding layer 500 a maybe formed between the barrier wall 161 e and the dielectric layer 161 b.

The metal shielding layer 500 a allows an electric field formed by theassembly electrodes to be formed only in the recess. As compared with anelectric field E1 described in FIG. 14 , it can be seen that an electricfield E2 formed in FIG. 16 is concentrated only in the recess.

An insulated state must be maintained between the metal shielding layerand the assembly electrodes. When the metal shielding layer and theassembly electrodes are electrically connected to each other, the metalshielding layer cannot perform a shielding function. Accordingly, atleast one type of insulating material should be disposed between themetal shielding layer and the assembly electrodes so that the insulatedstate between the metal shielding layer and the assembly electrodes ismaintained.

When the metal shielding layer 500 a is disposed as shown in FIG. 16 ,only the dielectric layer 161 b is present between the metal shieldinglayer 500 a and the assembly electrodes 161 c. The dielectric layer 161b should be formed to have a sufficient thickness to maintain theinsulated state between the metal shielding layer 500 a and the assemblyelectrodes 161 c.

In another embodiment, referring to FIG. 17 , the barrier wall 161 e mayhave a first surface in contact with the dielectric layer 161 b and asecond surface opposite to the first surface, and the metal shieldinglayer 500 b may be disposed to cover the second surface. The metalshielding layer 500 b may be disposed on an upper surface of the barrierwall 161 e.

In this case, the metal shielding layer 500 b may improve durability ofthe assembly substrate. Specifically, when the assembly substrate isused for the self-assembly multiple times, the barrier wall may bebroken due to external pressure. When the metal shielding layer 500 bcovers the barrier wall, the metal shielding layer 500 b can preventbreakage of the barrier wall 161 e due to external pressure during therepeatedly performed self-assembly.

With the structure according to FIG. 17 , since two types of insulatinglayers (the barrier wall and the dielectric layer) exist between themetal shielding layer 500 b and the assembly electrodes 161 c, theinsulated state between the metal shielding layer 500 b and the assemblyelectrodes 161 c is maintained.

The metal shielding layer 500 b allows an electric field formed by theassembly electrodes to be formed only in the recesses. It can be seenthat an electric field E3 formed in FIG. 17 is concentrated only in therecesses when compared with the electric field E1 described in FIG. 14 .

In another embodiment, referring to FIG. 18 , the barrier wall includesa first barrier wall 161 e′ formed on the dielectric layer 161 b and asecond barrier wall 161 e″ formed on the first barrier wall 161 e′, andthe metal shielding layer 500 c may be disposed between the first andsecond barrier walls 161 e′ and 161 e″.

Since the first and second barrier walls 161 e′ and 161 e″ cover bothsurfaces of the metal shielding layer 500 c, respectively, it ispossible to prevent the metal shielding layer 500 c from being oxidizedby contact with the fluid during the self-assembly.

With the structure according to FIG. 18 , since two types of insulatinglayers (the second barrier wall and the dielectric layer) exist betweenthe metal shielding layer 500 c and the assembly electrodes 161 c, theinsulated state between the metal shielding layer 500 c and the assemblyelectrodes 161 c is maintained.

The metal shielding layer 500 c allows an electric field formed by theassembly electrodes to be formed only in the recesses. It can be seenthat an electric field E4 formed in FIG. 18 is concentrated only in therecesses when compared with the electric field E1 described in FIG. 14 .

As described above, the metal shielding layer may be disposed on atleast one of the bottom of the barrier wall, an intermediate layer ofthe barrier wall, and the top of the barrier wall.

Meanwhile, the metal shielding layer may be disposed to overlap variousareas of the barrier wall, the assembly electrodes, and the baseportion.

The metal shielding layer may be disposed to overlap at least part ofthe remaining area, except for the areas where the recesses are formed,of the entire area of the barrier wall 161 e. When the metal shieldinglayer is formed in the recesses, it may be likely to interfere with theself-assembly, and thus the metal shielding layer is preferably disposedoutside the recess.

Meanwhile, the metal shielding layer may be formed on the edges of therecesses. A spacing may be generated between inner walls of the recessand the semiconductor light-emitting diode in a state where thesemiconductor light-emitting diode is mounted in the recess. Anunnecessary semiconductor light-emitting diode may be assembled in thespacing. The metal shielding layer disposed on the edge of the recessshields an electric field formed around the spacing, thereby preventingthe semiconductor light-emitting diode from being assembled into thespacing.

Meanwhile, the metal shielding layer may be disposed to cover gapsbetween the assembly electrodes. Specifically, an electric field isstrongly formed between the assembly electrodes. The recesses formed inthe barrier wall are formed between the assembly electrodes so that theassembly electrodes can strongly attract the semiconductorlight-emitting diodes. On the other hand, the areas where the recessesare not formed among the areas between the assembly electrodes arecovered with the barrier wall. Even if areas between the assemblyelectrodes are covered with the barrier wall, the semiconductorlight-emitting diodes may be mounted in the areas because the electricfield is strongly formed in the areas. That is, the semiconductorlight-emitting diodes may possibly be misassembled onto the surface ofthe barrier wall adjacent to the assembly electrodes. The metalshielding layer is disposed so as to cover the areas between theassembly electrodes where the electric field is strongly formed, therebypreventing the semiconductor light-emitting diodes from beingmisassembled onto the surface of the barrier wall.

In a detailed embodiment, referring to FIG. 19 , the metal shieldinglayer 500 d may be formed in a bar-like shape covering the area betweenthe assembly electrodes. In this case, one end of the metal shieldinglayer 500 d may be disposed on the edge of the recess formed in thebarrier wall. The metal shielding layer 500 d allows an electric fieldE5 to be formed only inside the recess.

In another embodiment, referring to FIG. 20 , the metal shielding layer500 e may be formed in an annular shape on the edge of the recess. Themetal shielding layer 500 e allows an electric field E6 to be formedonly inside the recess. The metal shield layer 500 e shields an electricfield formed around the spacing between the semiconductor light-emittingdiode and the inner walls of the recess, thereby preventing thesemiconductor light-emitting diode from being assembled into thespacing.

On the other hand, the sum of the thickness of the barrier wall and thethickness of the metal shielding layer in a direction perpendicular tothe assembly substrate is preferably smaller than the thickness of thesemiconductor light-emitting diode that is mounted in the recess. Partsof the semiconductor light-emitting diodes should be exposed to theoutside in a state where the semiconductor light-emitting diodes aremounted inside the recesses. When the semiconductor light-emittingdiodes mounted on the assembly substrate are transferred to the transfersubstrate by the method described with reference to FIGS. 10A to 10C,the parts of the semiconductor light-emitting diodes are exposed to theoutside, so that pressure applied by the transfer substrate can beconcentrated on the semiconductor light-emitting diodes.

As described above, since the assembly substrate according to thepresent disclosure comes with the metal shielding layer which completelyshields an electric field at unnecessary positions, the thickness of thebarrier wall does not need to be increased. Accordingly, the presentdisclosure enables the semiconductor light-emitting diodes to besmoothly separated from the assembly substrate during the process afterthe self-assembly.

What is claimed is:
 1. An assembly substrate comprising: a base portion;a plurality of assembly electrodes on the base portion; a barrier wallon the base portion; and a metal shielding layer on the base portion,wherein the metal shielding layer overlaps the barrier wall, wherein atleast one of the plurality of assembly electrodes is verticallyoverlapped with the barrier wall or the metal shielding layer, andwherein the barrier wall on the base portion comprises a plurality ofrecesses.
 2. The assembly substrate of claim 1, wherein the metalshielding layer is disposed to overlap at least part of a remainingarea, except for areas where the plurality of recesses is formed, of anentire area of the barrier wall.
 3. The assembly substrate of claim 1,wherein the metal shielding layer is disposed on edges of the pluralityof recesses.
 4. The assembly substrate of claim 1, wherein the assembly,substrate is used for a display device manufacturing method of mountingsemiconductor light-emitting diodes on the assembly substrate at presetpositions using an electric field and a magnetic field, wherein themetal shielding layer covers gaps between the plurality of assembly,electrodes, and wherein the plurality of assembly electrodes are notelectrically connected to the semiconductor light-emitting diodes. 5.The assembly substrate of claim 1, further comprising a dielectric layeron the base portion to cover the plurality of assembly electrodes,wherein the metal shielding layer is disposed between the barrier walland the dielectric layer.
 6. The assembly substrate of claim 5, whereinthe barrier wall comprises: a first barrier wall on the dielectriclayer; and a second barrier wall on the first barrier wall, wherein themetal shielding layer is disposed between the first barrier wall and thesecond harder wall.
 7. The assembly substrate of claim 5, wherein thebarrier wall comprises: a first surface in contact with the dielectriclayer; and a second surface opposite to the first surface, wherein themetal shielding layer is disposed to cover the second surface.
 8. Theassembly substrate of claim 1, wherein the assembly substrate is usedfor a display device manufacturing method of mounting semiconductorlight-emitting diodes on the assembly substrate at preset positionsusing an electric field and a magnetic field, and wherein a sum of athickness of the barrier wall and a thickness of the metal shieldinglayer in a direction perpendicular to the assembly substrate is smallerthan a thickness of one of the semiconductor light-emitting diodesmounted in a recess of the barrier wall.
 9. An assembly substrate usedfor a display device manufacturing method of mounting semiconductorlight-emitting diodes on the assembly substrate at preset positionsusing an electric field and a magnetic field, the assembly substratecomprising: a base portion; a first assembly electrode and a secondassembly electrode being spaced apart and extending in one direction anddisposed on the base portion; a dielectric layer stacked on the baseportion to cover the first and second assembly electrodes; a barrierwall on the base portion and having a plurality of recesses for guidingthe semiconductor light-emitting diodes to the preset positions; and ametal shielding layer on the base portion, wherein the metal shieldinglayer overlaps both the first assembly electrode and the second assemblyelectrode, and wherein the first and second assembly electrodes arevertically overlapped with one of the semiconductor light-emittingdiodes or the metal shielding layer.
 10. The assembly substrate of claim9, wherein the metal shielding layer is formed in an annular shape onedges of the plurality of recesses, and wherein a bottom most surface ofthe metal shielding layer is disposed higher than a top surface of thebase portion.
 11. The assembly substrate of claim 9, wherein the metalshielding layer is formed in a bar-like shape covering an area betweenthe first and second assembly electrodes, and wherein the first andsecond assembly electrodes are not electrically connected to thesemiconductor light-emitting diodes.
 12. The assembly substrate of claim9, wherein the metal shielding layer overlaps the barrier wall so thatthe electric field formed between the first and second assemblyelectrodes is shielded.
 13. The assembly substrate of claim 9, wherein asum of a thickness of the barrier wall and a thickness of the metalshielding layer in a direction perpendicular to the assembly substrateis smaller than a thickness of one of the semiconductor light-emittingdiodes mounted in one of the plurality of recesses.
 14. The assemblysubstrate of claim 9, wherein the barrier wall comprises: a firstbarrier wall on the dielectric layer; and a second barrier wall on thefirst barrier wall.
 15. The assembly substrate of claim 14, wherein themetal shielding layer is disposed between the first barrier wall and thesecond barrier wall.
 16. The assembly substrate of claim 9, wherein thebarrier wall comprises: a first surface in contact with the dielectriclayer; and a second surface opposite to the first surface.
 17. Theassembly substrate of claim 16, wherein the metal shielding layer isdisposed to cover the second surface.
 18. The assembly substrate ofclaim 9, wherein one type of the dielectric material is disposed betweenthe metal shielding layer and the first and second assembly electrodes.19. An assembly substrate comprising: a base portion; a plurality ofassembly electrodes on the base portion; a barrier wall on the baseportion; and a metal shielding layer on the base portion, wherein themetal shielding layer overlaps the barrier wall, wherein at least one ofthe plurality of assembly electrodes is vertically overlapped with thebarrier wall or the metal shielding layer, wherein an electric fieldbetween the plurality of assembly electrodes is shielded by the metalshielding layer overlapping the barrier wall, and wherein a bottom mostsurface of the metal shielding layer is disposed higher than a topsurface of the base portion.